1. Field of the Invention
The present general inventive concept relates to an image forming apparatus, and more particularly, to an image forming apparatus that uses a developer, a developing unit thereof and a method of controlling the developing unit.
2. Description of the Related Art
An image forming apparatus is an apparatus that prints a black and white image or a color image on a printing medium, e.g., paper, according to an inputted image signal, for example, a laser printer, an ink-jet printer, a copying machine, a multi-function printer, a fax machine, etc. An image forming apparatus is classified as an electrophotographic type in which a beam is scanned onto a photosensitive body to form an electrostatic latent image and a toner is adhered to the electrostatic latent image to transfer the same onto a printing medium, or an ink-jet type in which a liquid type ink is ejected onto a surface of a printing medium according to an image signal.
The electrophotographic image forming apparatus is configured such that a surface of a photosensitive body is charged with a predetermined electric potential, a beam is scanned onto the photosensitive body to form an electrostatic latent image due to electric potential difference, and a developer, i.e., a toner is adhered to the electrostatic latent image to form a visible image. The visible image formed on the photosensitive body is transferred onto the printing medium, and is fixed to the surface of the printing medium by applying heat and pressure to the printing medium.
The electrophotographic image forming apparatus uses a unitary developer which is composed of an insulating toner or a conductive toner, or a binary developer which is composed of a toner and a magnetic carrier. The electrophotographic development using the unitary developer is achieved such that toner particles are charged by friction between the toner particles or friction with a charging member and are transferred onto a photosensitive body through a developing roller. The electrophotographic development using the binary developer is achieved such that a magnetic carrier and a non-magnetic toner of a synthetic resin material are mixed in the appropriate ratio, toner particles are charged when mixed with carrier particles, and the toner particles and the carrier particles are transferred onto the photosensitive body through a magnetic roller.
The development using the binary developer has the merit that a toner charging efficiency is high, a lifespan of the toner is long, and deterioration of toner quality during the charge is low, resulting in an increase in image quality.
A developing unit of an image forming apparatus using the binary developer includes a housing which has a space to agitate the toner, a magnetic roller which receives the agitated toner and attaches the same to a photosensitive body, and a pair of augers which are mounted in the housing to agitate the toner. The housing is provided with a toner supply port, through which the toner is supplied from a toner supply container mounted to the exterior of the housing. A space inside the housing is sectioned into an agitating space in which the toner is mixed with the carrier, and a supply space from which the toner mixed with the carrier is supplied to the magnetic roller. One auger is rotatably mounted in the agitating space, and another auger is rotatably mounted in the supply space. The agitating space and the supply space can be communicated with each other by two gates which are provided at both sides of the inside of the housing.
While a new toner supplied into the agitating space of the housing is transferred toward one side of the housing by the auger mounted in the agitating space, the toner is mixed with the carrier and simultaneously charged. The developer mixed in the agitating space is transferred into the supply space through the gate provided at one side in the housing, and is adhered uniformly to the surface of the magnetic roller while being transferred toward the other side of the housing by the auger mounted in the supply space. The developer transferred to the other side of the housing without being supplied to the magnetic roller is transferred again into the agitating space through the gate provided at the other side of the housing.
However, in the above conventional developing unit of the image forming apparatus, the developer may be concentrated on one of the gates due to the tilting during conveyance or installation, or the irregular operation of the augers. In this case, because the developer cannot be transferred smoothly through the gates, a transfer pressure of the developer at the gate increases and a torque of the rotating auger increases excessively, which may cause breakage of the components like the auger or the housing.